Overproduction of gamma interferon in B/Jas inbred rabbits with herpes simplex virus encephalitis

Inbred rabbits of the B/Jas strain are highly susceptible to herpes simplex virus type-1 (HSV-1) encephalitis, developing seizures of encephalitis aft er intravenous injection of the KOS strain of the virus. Anti-viral interfe ron activity became detectable in the serum just prior to or at the onset o f seizures, its level being lower in the serum than in the cerebrospinal fl uid. The activity was of gamma interferon, as suggested by the acid instabi lity and the inability of Mx protein induction. An immunohistochemical anal ysis of the brain tissues of encephalitic rabbits showed that MHC class I a ntigen was expressed on the microglia cells of inflamed lesions but not on these cells in uninflamed areas. These findings were discussed in correlati on with the pathogenesis of herpetic encephalitis in the inbred rabbits.